The present invention relates to an innovatory armchair structure of the type provided with a footrest and a back that are movable by electric motors.
Further motor-driven transmission mechanisms are disclosed by U.S. Pat. No. 3,934,929, wherein a worm screw actuator is connected on one ends the seat of the chair and on the other to the backrest, and by DE-U-8904979, wherein the movement of chair portions is obtained thanks to a motor unit extending between a fixed frame and the backrest.
Well known in the art are armchairs having a footrest and a back adapted to be drivingly inclined by means of electric motors. For strength and economy purposes the so-called xe2x80x9cdual motorsxe2x80x9d are very used; they are made up of a monolithic unit of a generally rectangular shape having two motor reducers inside it, the rotation shafts of which project close to the two ends of the unit.
The dual motor is mounted on a fixed frame of the armchair for extending longitudinally thereof, with a rotation shaft which is close to the back and the other rotation shaft which is close to the footrest. Crank mechanisms connect each rotation shaft to the respective element (back or footrest) to be moved.
Usually, the rear shaft controls movement of the back, whereas the front shaft simultaneously controls movement of the footrest and the base seat, in terms of lifting the base seat (pivotally mounted, at the back, to the fixed frame) at the front, as the footrest itself moves upwardly.
For movement transmission, kinematic connecting rod-crank mechanisms connect the rear shaft to the back and the front shaft to the footrest and the base seat.
This structure is rather complicated, relatively expensive and bulky.
In addition, the inclination movement of the base seat should have to be used for maintaining a given angle between the bust and the pelvis when the back is greatly inclined. However, due to the fact that the base seat movement is only connected to the footrest movement, this effect cannot be reached if the footrest is left at its lowered position or at all events it is not completely raised.
But, when the footrest is even only partly lowered there is the maximum requirement of keeping an angle between the seat base and the back for avoiding too much stress at the lumbar region.
In the opposite case too, if the footrest is wished to be raised leaving the back at its completely lifted position, too much stress may be caused at the lumbar region. In fact, since the base seat movement is connected to the footrest movement, by raising the footrest, the angle between the base seat and the back is simultaneously reduced. If the back is completely raised, this angle may become too small for a comfortable position.
A further undesirable effect present in the above-mentioned known art is that of having a distance between the front shaft and the footrest which increases on increasing of the base seat inclination, because the footrest is hinged on the front edge of the base seat and moves therewith, whereas the motor is fixed to the ground.
As a result, the driving shaft must have a relatively high rotation angle for completely raising the footrest, so as to compensate for the progressive moving away of the hinging points of the kinematic connecting rod-crank transmission mechanism between the driving shaft and the footrest.
Further motor-driven transmission mechanisms are disclosed by U.S. Pat. No. 3,934,929, wherein a worm screw actuator is connected on one end to the seat of the chair and on the other end to the backrest, and by DE-U-89 04 979, wherein the movement of chair portions is obtained thanks to a motor unit extending between a fixed frame and the backrest.
It is a general object of the present invention to eliminate the above mentioned drawbacks by providing an armchair with power-driven footrest and back, which has an innovatory kinematic movement structure with a dual motor. In view of the above object, in accordance with the invention, an armchair has been devised which comprises a support frame to which a base seat, a back and a footrest are fastened, which elements are movable between a first and a second positions through power-driven movement means, characterized in that the power-driven means is suspended from said base seat and movable therewith.
An armchair structure has also been conceived, in which the base seat is pivotally mounted at the front on the support frame according to a first transverse axis, on said base seat being pivotally mounted the back, at the rear thereof, according to a second transverse axis for rotation of the back, the back having extensions extending downwardly past said second axis and having ends constrained to slide longitudinally of the armchair, so that on rotation of the back about said second axis, the base seat rotates in the same way about said first axis.